diff --git a/math/proof/notes.page b/math/proof/notes.page
index 3d2cc4f..d3d8bc9 100644
--- a/math/proof/notes.page
+++ b/math/proof/notes.page
@@ -218,15 +218,13 @@ $$ so $\overline P$ is the set of composite numbers and 1.
 
 $A_1, A_2,\dots, A_n$ are sets.
 
-$$
-\begin{align}
+$$\begin{align}
 A_1 \cup A_2 \cup A_3 \cup \dots \cup A_n &=
-\left{x : x \in A_i
+\left\{x : x \in A_i
   \text{ for at least one set $A_i$, for }
-  1 \leq i \leq n\right}\\
+  1 \leq i \leq n\right\}\\
 A_1 \cap A_2 \cap A_3 \cap \dots \cap A-n &=
-\left{x : x \in A_i
+\left\{x : x \in A_i
   \text{ for every set $A_i$, for }
-  1 \leq i \leq n \right}\\
-\end{align}
-$$
+  1 \leq i \leq n \right\}\\
+\end{align}$$